Municipalities and the like have extensive networks of piping to control the flow of water from storage and pumping stations to users. The network of piping includes numerous valves such that portions of the network can be closed off as needed for service while the remainder of the network remains in operation. The piping required for such networks can range in size from as small as three or four inches in diameter to as large as three feet in diameter. Also, the valves of the system typically remain in an open condition or in a closed condition for very long periods of time. The valves of a municipal water system are located below ground with an access shaft extending from the valve stem to the surface through which an elongate key is extended to turn the stem. Such valves typically include a screw that is rotatable through one hundred turns or more to fully open or fully close the valve. Also, underground valves undergo a certain degree of deterioration over time and it is common for valves to become frozen or locked into their current position as a result of contamination on the surface of the screw or deterioration of the parts. As a result, the large amount of torque needed to open and close such valves is provided by a motorized valve operating machine. Such machines are heavy and awkward and when operated apply a great amount of torque to the key that extends down a shaft to the valve stem for rotating the valve. Accordingly, to aid in the operation of such valve turning machines it is common to mount such valve turning machines on an arm attached to a truck.
One such mounting device shown in U.S. Pat. No. 6,009,905 to Arnemann is to mount the valve turning machine on a horizontal slide that allows the machine to move horizontally from a first position over the truck bed to a second position spaced from the side of the truck. Such slideable mounting provides rigid support to the valve turning machine while it exercises a valve. The longitudinally slideable structure, however, has limited mobility with respect to the vehicle. Where valves are positioned between various obstacles such as buildings, curbs, boulders, trees and the like, it may not be possible for the truck to reach a position where the valve operating machine may be positioned directly over the shaft leading to the valve.
Efforts have been made to attach a valve operating machine to a manipulating arm connected to a truck. One such device is sold under the trademark SPIN DOCTOR by Hurco Technologies, Inc. and disclosed in Hurley, U.S. Pat. No. 7,334,606 B1. The Hurley device includes a multi-hinged arm configured as a backhoe with the inner end of the arm connected to a vehicle and the outer end to a valve turning machine. The arm is pivotable about a horizontal axis generally giving the device a hundred and eighty degree range of rotation with the hinged elbow of the backhoe arm permitting the free end of the arm to move eight to twelve feet radially outward of the vehicle. The hinged elbow includes one or more spring loaded compensating structures to apply a vertically upward force to the free end of the arm to compensate for the weight of the valve turning machine. By virtue of the spring loaded compensating devices, the free end of the arm can be manipulated to a position directly over an otherwise difficult to reach shaft to a valve.
It has been found that a valve turning machine mounted on the Hurco arm is attached by a key to a valve and with torque applied to the key by the machine, the machine will shake and toss violently as the valve is exercised. The shaking and tossing is a result of the uneven torque applied to the key as the turning screw encounters areas of contamination by foreign materials and deterioration of the moving parts. The shaking and tossing of the machine includes vertical components of force which cause the key to be pulled free of the valve stem thereby interrupting the valve turning operation and perhaps causing damage to either the machine or the valve. To retain the machine and the key in their desired orientation with respect to the valve stem, the operator is required to grasp the machine with his arms and use his body weight to hold the machine in the desired orientation as the valve is exercised. Since the shaking and tossing of the machine is caused by contamination and deterioration below ground and not visible to the operator, the movement of the machine is unpredictable and can also cause injury to the operator. Accordingly, there is a need for providing an extendable arm for supporting a valve operating machine over a valve stem positioned remotely from a vehicle that will retain the machine against all the forces applied to the end of the arm as a consequence of frequent and sudden changes in torque applied to the valve.